Why did a number of incidents not automatically change queue and escalate per our rules?

Environment:

Business Rules, Escalation Rules, Revalidate option

Issue:

We recently discovered a large number of incidents in the wrong queue, significantly out of SLA. They should have been escalated by rules. Those incidents did not automatically change the queue.

Resolution:

If you have the "Revalidate" option checked for the escalation rule, this revalidation process will check the conditions each time the incident is updated. The important thing to note is that if the escalation rule is contained in a function, the conditions that are revalidated include the conditions in the rule which calls this escalation function.

For example, in the following scenario:

In State "02. In progress"
Rule: "Call Escalation Function"
If condition:  incident.status = "Escalate"
Then: Call "Escalation Function"

Functions: "Escalation Function"
Rule: Escalation Chain rule
If conditions:  incident.status in "Escalate, Updated"
Then: set escalation level +1 hour from now (Revalidate)

If an incident is created and set to a status of  "Escalate", the incident triggers the "Call Escalation Function" which triggers the "Escalation Chain Rule". This rule sets up a pending action to set the escalation level in one hour. If the customer updates the incident before the hour is up, the status gets set to Updated. The conditions of the escalation are revalidated at this time.

The conditions which are checked in the above example are:
     If condition:  incident.status = "Escalate"
     If condition:  incident.status in "Escalate, Updated"

Since the status is Updated, the second condition is met but the first is not. The pending escalation action criteria is considered no longer valid and is removed.

It's generally a better practice to have your conditions in the escalation rule inside the function instead of the rule which calls the function.